Patent Literature 1 discloses a nonvolatile switching device. FIG. 8 shows the prior nonvolatile switching device disclosed in FIG. 3 of Patent Literature 1.
As shown in FIG. 8A, the nonvolatile switching device comprises a substrate 11, a control electrode 12, a ferroelectric layer 13, a semiconductor layer 14, and first to third electrodes 15a-15c. The control electrode 12, the ferroelectric layer 13, and the semiconductor layer 14 are stacked in this order on the substrate 11. The first to third electrodes 15a-15c are provided on the semiconductor layer 14.
A voltage is applied between the control electrode 12 and the first to third electrodes 15a-15c to change the polarization direction of the ferroelectric layer 13.
In a case where a portion of the ferroelectric layer 13 has upward polarization direction, the portion of the semiconductor layer 14 stacked on this portion of the ferroelectric layer 13 has low resistance. This corresponds to the ON-state.
On the contrary, in a case where a portion of the ferroelectric layer 13 has downward polarization direction, the portion of the semiconductor layer 14 stacked on this portion of the ferroelectric layer 13 has high resistance. This corresponds to the OFF-state.
In FIG. 8A, only the portion of the ferroelectric layer 13 positioned below the third electrode 15c has the downward polarization direction. Accordingly, as shown in FIG. 8B, a current flows selectively from the first electrode 15a to the second electrode 15b. 